Most bonsai are made from hardy trees and plants, decreasing the risk of bonsai pests and disease. Both of these will occur though, so it is important to know what to do. The process of identifying the pest or disease is very important and if the right diagnosis occurs, a suitable remedy can be applied.
Keep in mind pesticides can be dangerous and most bonsai experts would recommend using them as a last resort. If you do use pesticides of fungicides, ensure you follow the instructions and wear appropriate protective gear.
This article will focus on bonsai pests. Keep an eye out over the next week or two for an article on bonsai disease.
Common Bonsai Pests
can be a serious problem due to the fact they will inhabit plants and suck the sap from stems, leaves and fruit. They love early, tender spring growth.The first signs you have an infestation of aphids is usually indicated by the leaves starting to curl up and change shape. Aphids come in an array of colors with the most common being black, white and green and appear on the underside of leaves.
The woolly aphid can be an issue particularly on pine and larch where it is difficult to remove from between the needles without applying an insecticide.
Red Spider Mites
are tiny spider like mites that will attack your bonsai. Spider mites can turn your bonsai leaves from green to yellow, and then brown if left untreated, and even make your bonsai wither and die. You will also notice fine webs, which they weave in order to lay their eggs. Because mites are barely visible, the best way to confirm their presence is to shake a branch over a piece of white paper.
image Reference: Environmental Farmers Network
can be difficult to see until the shell starts lifting showing a fluffy and sticky white substance. Scale insects can be difficult to eradicate. Systematic insecticides will be your best bet preventing these becoming a problem for your bonsai. If you only have a small infestation, brushing with an implement like a tooth brush will remove from the trunk, however care needs to be taken they do not fall into the soil and then later reappear.
Image Reference: Environmental Farmers Network
the many varieties caterpillars are common bonsai pests which can attack the leaves and shoots of your bonsai. Due to excellent camouflage, they are often difficult to spot, until you notice leaves which have holes or ones that are completely stripped. The best way to fight off these pests is to inspect your plant manually and remove the caterpillars by hand. Make sure to check the underside of leaves which are the common hiding spots of caterpillars.
Image Reference: EcoGrow
are difficult to eradicate, with the larvae eating the root system of your bonsai which is of course your trees lifeline. When you repot your bonsai, inspect the roots for larvae, washing any off and destroying them. Adults vine weevil is also difficult to spot as they come out only at night to feed on your trees leaves. A soil insecticide will kill the larvae, however if you suspect vine weevil, you will need to inspect your tree at night with a torch.
Though treatment solutions are readily available for various bonsai pests, observing your bonsai is still the most effective measure in preventing problems from taking place. Every bonsai grower is encouraged to learn how to recognize potential problems quickly and perform bonsai ‘first aid’ as soon as possible to improve the chances of recovery and to prevent the bonsai pests from spreading.